Dynamic braking system for series motors



Feb; 17, 1948. G. PURIFOY 2,436,330

DYNAMIC BRAKING SYSTEM FOR SERIES MOTORS Filed Feb. 28, 1946 2 Sheets-Sheet 1 Ma for/n INVENTOR eo/ye E un/0y,

Feb. 17, 1948. PURIFOY 2,436,330

DYNAMIC BRAKING SYSTEM FOR SERIES MOTORS Filed Feb. 28, 1946 2 Sheets-Sheet 2 WITNESSES:

INVENTOR '6 0 53/ 'o 59715 e rye rz/V Patented Feb. 17, 1948 UNITED sTArrEs oFFIcE DYNAMIC. BRAKING sr'srrm Fort George R; Pu'rifoy; Pittsburgh; rPaz assignor to Westinghouse Electric Qorporation;eEast-Pitts burgh; Pa-.-,-a corporation of Pennsy lvania" Application rebrusryzs, 1946;- SeriaINo; 650,949

, 1' v My inventionrelates? ge' "erally', to control sys terns and, more particularlyg: to 'systems for com trolling the' operation of the propelling motors of electricyehicles and the like. I

An object of my invention, generally stated} is to provide a control system' which-shall be simple and efficient inoperationand which mayfb'e eco' I nomica'llymanufactured andfinstalleda A morespeciiic' object or my 'inventlo'n' isto; control the buildingwp of dynamicbrakin'g' of an electrically propelled"'vehic1e 7 Another object 'ofn'iy iiiventiori is-to revent overvoltage ofthe motors during dynamic brak Other objects of myinventlon willbe explained fully hereinafter" or wilfbe apparent 'to' those skilled in'the art.

In accordancewithmne embodiment of my' -in vention, the operation ofthe" field" shunting" switches for themotors -of a-'vehic'le'is 50- con-- trolled by a current limit relay that the-dynamic braking 1 current and hen'ce the motor" volt'age' are" limited to a safe'valuei- Starting of-the' progrs: sion of the braking resistor shunting meansis controlled 'by'the field shunting switches-.

For a fuller understanding o'fth'e 1 nature and objects of'myinventiomreference maybe had to the following detailddscriptiom taken'in' con'-* junction with the accompanying"drawings; in

which:

Figures 1A and j 1B} when combined; =consti-- tute a diagrammatic'view of acon'trol system'einbodying the principal features ofmy'invention and I Fi'g.'2 is a 'chart-showingthe sequenceiot operation of'part of the apparatus illustrated in 1A and "13.

Referring to the drawingsfia pair of'motof's and "I I may be'utilized -ior propelling a vehicle" (not shown) The-motor I Wis" pro'vided'wi'thmn i armature winding l2 and a series-field winding e I3. Likewise, th'e' motor' II isprovidedwitl'r'an station (not shown) The motors 'l u andil I "are connectediri parallel circuit relation during acceleration ofthe vehicle.

They may also be connected' for dynam ic'brakingzr 2 df m'otor' 'I O and the-mew" In order to provide for changing the setting or" 10 Glaim's.: (c1. sic-sci) current-'ln tlie aiinatiire's'to'reverse and cause the motors te- 'act 1 as: generators and decelerate' the I vehicle? x pairpf switches BI and B2 is provided for establishin the'idyhami braking. con; :7 nectionsi'z v The :aceereratorm comprises a circular bus I8;

inside otiwhich are 'dispos'ed a I lurality of con-- sivelyi foiced against' -th'e i has l8 by a' pairof" ilirevolvin'g rol'ler's IIl-and 20.

The rol l'ers I9" and- 20 are driven by a pilot motorPMi'thi ougha shaft-4i. The pilot motor PM is provided with an armature winding 44 andtwo'fiel'd win'di'hgs 45 and 45;on'e for each direction source of-eontrbl energy:

A limit relay-LR is providedior controlling the op'eration'of the pilotm'otor PM during both ac AS? shown',-the relay LR 'isprovided with several dif fereri't acti-iating colls which function to operate" the-relay 'duriiig accelerationand dynamic brak ing; Thus, a*-series coi-l Al is-connected in the celeration' and'deceleration of themotor.

11101301 Circuit during th 7 acceleration and decelration of the vehiclep- A variable rate coil 48 isf energized during acceleration anddynamic' brak ing fofcontrolling the accelerating and brakthe relay in a manner well' known in the art.

therelay'LRi thereby governing the rates of accelerati'onandtleceleratiori of the vehicle by vary ing the s-pe'ed 'of the pilot motor PM, whichiri' turn, controls the rate at which resistance is shunted -frorn the motor circuit'to vary the motor currentvariableresistors 52: and 53 are connected-in the energizingircuit for" the rate coil 48; The resistors 52 and 53 are varied by'means "5930f a'master'scontroller MC which maybe dividedinto two sections, one "designated-AC, which is utilized during acceleration or: the vehicle," and lng idynamie braking'rofi thevehicl'e;

armature I 5 0i i iiotdr I'," thereb'y permitting' tli'e "55- controlle'r '1s operatedby' the 1 operator "ot the 've.

-Boththe acceleration and the deceleration' of the motors I 0 and I l are 'priinarily controlled'by a" motor d'rlverfacceleratonA which is of the same" general type Iasthe one described in Patent No. :1,991,229;issuedr'eomary 12,1935, to L. G. Riley."

-oi-'rotatiori*of the motor; f The energy for operating the pllot' mot'or and -'the control apparatus may besuppli'ed by a battery or other suitable f ing rates; A- coil '49 may be energized from the control'sour'ce' to aldlfl the operatlon'ofthe-relay, anda tickler'coil" 5| may also be energized fromthe'control source to cause-a'vlbratOry action of iiicie, the accelerating and braking rates may be varied by the operator as desired.

The accelerator A is provided with resistors 56 and 55 for controlling the current in the motors i and II. The resistor 54 is divided into a number of subdivisions which are connected to the contact fingers It to 30, inclusive, and the resistor 55 is divided into subdivisions which are 1 connected to the contact fingers 3! to es, inclusive. In the present system, the resistors 54 and 55 are connected in the motor circuit in series-circuit relation during both acceleration and dynamic braking, thereby making it unnecessary to change the resistor connections when transferring from motoring to braking operation.

, preparation for an establishment of the dynamic braking circuit for the motors when the switch M2 is closed to connect the motors I0 and H directly As described in Patent No. 2,254,911, issued September 2, 1941, to L. G. Riley, resistors 56 and 5'! are connected in the motor circuit in parallelcircuit relation to the resistors 54 and 55 during the motoring operation. Since part of the motor current is diverted through the resistors 58 and 5?, the heating effect on the accelerator is reduced and also arcing of the contact fingers on the .accelerator is reduced.

As shown, the accelerator A is provided with a drum switch 58 having a, plurality of contact segments 6| and 61, inclusive, and cooperating contact fingers which engage the contact segments as the accelerator is driven by the shaft M, The reference numerals 2| to 30' indicate the contact fingers over which the roller l9 travels while the contact segments are engaged by their respective contact fingers. It will be seen that the roller travels over the fingers 3| to 48 while the roller l9 travels over fingers 2| to 36. The function of the difierent segments of the drum to ground through the switch G after the accelerator has been fully advanced to shunt its resistance from the motor circuit.

As described in my Patent 2,318,332, issued May 4, 1943, interlocks are provided on the switch R, for so controlling the operation of the pilot Y are closed to connect the motors to the power After the car has started moving and the rate of acceleration is to be increased, it is only necesswitch 58 will be explained more fully hereinafter.

In addition to the accelerator and the control switches previously mentioned, numerous other motor PM that the accelerator may be stopped and held on any position by operating the switch R which is controlled by the accelerating controller AC. Thus, the controller AC is provided with a switching position and variable rate positions.

When the controller AC is actuated to the switching position, the switches LSI, MI and G circuit in series-circuit relation with the resistors 54 and 55 of the accelerator A and also in seriescircuit relation with the resistor 68. At this time,

the accelerator A will remain in its initial position.

sary to actuate the controller AC to one of the rate positions, thereby closing the switch R to 1 connect the resistors 56 and 51 in parallel circuitrelation to the motors and also closing the switch LS2 to shunt the resistor 68 from the motor switches are provided and perform certain switching operations. shunting a resistor 68 from the motor circuit, a switch Ml for connecting the motors to the accelerator during acceleration of the vehicle, a switch G for connecting the accelerator resistors to ground during acceleration, a switch M2 for These include a, switch LS2 for connecting the motors directly to ground through the switch G after the accelerator resistors have been shunted from the motor circuit by the accelerator rollers, a switch R for connecting the resistors 56 and 51 in the motor circuit during acceleration as previously described, and field shunting switches SI, S2 and S5 for shunting the field winding l3 of the motor I 0 and also field shunting switches S3. S4 and S6 for shunting the field I5 of the motor 14 in successive steps, as will be explained more fully hereinafter. Preferably, the field shunting switches are utilized to so control the building up of the dynamic braking current that overvoltage of the motors is prevented, particularly when the vehicle is running at high speeds when dynamic braking is applied. The operation of the field shunting switches is controlled by the limit relay LR to prevent an excessive current, and, therefore, prevent excessive voltage being developed in the motors. Furthermore, the accelerator A cannot start progressing to shunt the resistance from the motor circuit until after the successive operation of the field shunting switches is completed. a .In order to permit the present system to b utilized on cars which are operated in multipleunittrains and controlled from one control station at thehead oi, the train, a braking relay BR circuit. The closing of the switch R causes the accelerator to rotate, since the pilot motor is energized through interlocks provided on the switch R, as will be described more fully hereinafter.

If it is desired to stop and hold the accelerator on any given position, the controller AC is returned to the switching position, thereby opening the switch R to deenergize the pilot motor and stopping the accelerator at the desired position. The opening of the switch R also slightly increases the total resistance in the motor circuit to provide a cushioning efiect on the motors.

thereby providing smoother operation of the vehicle.

Thus, by opening and closing the switch R, the accelerator A is caused either to progress or to hold on a desired position. If automatic acceleration is desired, it is only necessary to actuate the controller AC to any desired rate position and the progression of the pilot motor will be under the control of the limit relay LR.

The foregoing feature is particularly desirable when operating a vehicle through congested traific areas which require that the acceleration 1 of the vehicle be interrupted frequently. Furthermore, the slight increase in the resistance in v the motor circuit caused by the opening of the switch R and the switch LS2 in the foregoing manner, prevents jerking or jumping of the cars during acceleration, as the progression of the accelerator is stopped at a desired running speed.

In order that the functioning of the foregoing apparatus maybe more clearly understood, the

operation of the system will now be described inmore detail. As explained hereinbefore, power :switches SI, S2, S3, S4, S and S6 are closed to shunt the field windings I3 and I5 of the motors I9 and II, respectively.

The energizing circuit for the switch SI may be traced from positive through a contact segment I2] on the controller AC, conductor I28, an interlock I29 on the switch ,G, conductor I22, the interlock I2I on the switch B2, conductor III, the actuating coil of the switch SI and thence to ground through a circuit previously traced. The energizing circuit for the switch S3 extends from the conductor I I1 through the actuating coil and thence to ground as previously traced. The energizing circuit for the switch S2 extends from the conductor I22 through the interlock I23 on the switch B2, conductor I24, the actuating coil ofthe switch S2 and thence to ground through a circuit previously traced. The energizing circuit for the switch S4 extends from a conductor I24 through the actuating coil and thence to ground as previously traced. The energizing circuit for the switch S5 extends from the conductor I22 through an interlock I 3I onthe switch B2, conductor I32, an interlock I33 on the switch G, conductor I34 and the actuating coil of the switch S5 to ground. The energizing circuit for theswitch S6 extends from the conductor I34 through the actuating coil of the switch to ground.

In the event that dynamic braking is required to decelerate the vehicle, the controller BC is actuated to one of the braking positions, thereby closing the switches BI and B2 to establish the dynamic braking connections. The energizing circuit for the switch BI may be traced from positive through a segment I35 on the controller BC, conductor I36, an interlock I31 on the switch LSI, conductor I38, the actuating coil of the switch BI, conductor I39 and a segment 63 on the drum switch 58 to ground. The energizing circuit for the switch B2 extends from the conductor I38 through the actuating coil of the switch B2 and thence to ground through the conductor I39 and the segment 63.

It will be noted that the accelerator A was returned to its initial position when both of the controllers AC and BC were actuated to their "oil" positions. The energizing circuit for operating the pilot motor PM in the reverse direction to return the accelerator A to its initial position may be traced from positive through an interlock I4I on the switch LSI, conductor I42, an interlock I43 on the switch BI, conductor II4, J -the segment 6'! on the drum switch 58, conductor II5, the off field winding 46 and the armature winding 44 of the motor PM to negative.

As previously explained, the field shunting switches SI to S6, inclusive, were closed when V both of the controllers AC and BC were actuated to the "01? position and these switches remain closed after the switches BI and B2 are closed to establish the dynamic braking connections, thereby preventing an overvoltage from being developed by the motors as a result of high speed operation of the vehicle. The holding circuit for the switches S2 and 84 extends from the conducthereby energizing the actuating coil of the reswitch S4 and conductor I24 to the actuating cOilS of the switches S2 and S4. The holding circuit for the switches S5 and S6 extends from the conductor I22 through an interlock I46 on the switch S4 and conductor I34 to the actuating coils of the switches S5 and S6. The holding circuit for the switches SI and S3 extends from the conductor I22 through an interlock I41 on the switch S5 to the conductor II! and thence to the actuating coils of the switches SI and S3.

.thespeed of the motors decreases, the current-lathe :limit relay LR will I decrease sufficiently to permit its contact members to close,

lay BR; The energizing circuit for therelay BR extends from the conductor 99 through an interlock I48 on the switch B2, conductor I49 and the actuating coil of the relay BR to ground.

The energization of the actuating coil of the relay BR opens its contact members to interrupt the circuit from the conductor I22 to the conductor I44, thereby causing the switches S2 and S4 to open. The opening of the switches S2 and S4 decreases the field shunting effect on the motors, thereby permitting the motor current to increase which opens the contact members of the limit relay LR, thereby deenergizingthe relay BR. As the switch S4 opens, the holding circuit for the switches S5 and S6, which previously extended from the conductor I22 through the interlock I46 on the switch S4 to the conductor I34, is transferred to a circuit extending from the. conductor I22 through the contact members of the relay BR to the conductor I 44, an interlock I5I on the switch S5, conductor I52 and an interlock I53 on the switch S4 to the conductor I34.

When the motor current again decreases sufficiently to permit the contact members of the relay LR to close, the relay BR is energized to open its contact members, thereby deenergizing the actuating coils of the switches S5 and 86 by interrupting the holding circuit previously traced. The opening of the switches S5 and S6 causes the motor current to increase, thereby operating the limit relay LR to .deenergize the relay BR as previously described.

When the contact members of the relay BR are reclosed, the holding circuit which previously extended from the conductor I 22 through the interlock I41 on the switch S5 to the conductor I I1 and the actuating coils of the switches SI and vS3 is transferred from the conductor through the contact members of the relay BR to the conductor I44, an interlock I54 on the switch SI, conductor I 55 and an interlock I56 on the switch S5 to the conductor II'I.

When the motor current decreases sufiiciently to permit the contact members of the relay LR to close, the relay BR is energized to open its contact members, thereby deenergizing the actuating coils of the switches SI and S3 causing these switches to open as the limit relay functions for the third time. In this manner, the field shunting effect on the motors Ill and II is reduced in three successive steps as the speed of the motors decreases, thereby preventing an excessive braking current and hence an overvoltage from being developed in case dynamic braking is applied while the motors are operating at high speeds.

Following the opening of the switch SI, an

energizing circuit is established for the pilot aaaacso motor PM to cause" this motor-to advance the accelerator A to shunt the resistors 54- and '55 from the motor circuit. The energizing circuit for the pilot motor may be traced from the conductor 99 through an interlock I51 on the switch SI, conductor I58, an interlock l'9 on the switch 132, conductor HM, an interlock I05 on the switch M2 and thence to the switch M2 and thenceto the pilot motor through a circuit previously traced.

As explained hereinbefore, the accelerator is advanced under the control of the limit relay during dynamic braking, thereby controlling the braking current by varying the resistance in the motor circuit. When the accelerator A is fully advanced at the end of the braking cycle, the actuating coil for the switch M2 is energized through a circuit established through an interlock it! on the switch B2 and the contact segment 62 on the drum switch 58. In this manner, the resistors 54 and 55 of the accelerator A are shunted from the motor circuit after the accelerator is fully advanced during dynamic braking and the accelerator is returned to its initial position in preparation for an accelerating cycle of operation.

From the foregoing description, it is apparent that I have provided a simplified and improved system for controlling the operation of railway vehicles which permits operation of field shunting switches to build up dynamic braking and prevents overvoltage of the motors when the vehicle is running at high speeds. While the present system is particularly suitable for utilization on vehicles operating in multiple-unit trains, it is not necessarily limited thereto and may be utilized on vehicles operating as single units.

Since numerous changes may be made in the above-described construction and difierent embodiments ofthe invention may be made without departing from the spirit and scope thereof, it is intended that all matter contained in the foregoing description or shown in the accompanying drawing shall be interpreted as illustrative and not in 9, limiting sense.

I claim as my invention:

1. In a motor control system, in combination, a direct current motor of the series type for propelling a vehicle, power conductors, switching means for connecting the motor to the power conductors, switching means for establishing dynamic braking connections for the motor, means for shunting the motor field during dynamic braking, relay means responsive to the motor current for controlling the operation of said field shunting means, and manually controlled means for changing the setting of said relay means to vary the dynamic braking rate.

2. In a motor control system, in combination, a direct current motor of the series type for propelling a vehicle, power conductors, switching means for connecting the motor to the power conductors, switching means for establishing dynamic braking connections for the motor, means for shunting the motor field when dynamic brakin; is established, relay means responsive to the motor current for controlling the disconnecting of said field shunting means, and manually controlled means for changing the setting of said relay means to vary the dynamic braking rate.

3. In a motor control system, in conibnation, a direct current motor of the series type for propelling a vehicle, power conductors, switching means for connecting the motor to the power conductors, switching means for establishu'lg, dy-

' I when dynamic braking is established, and relay means responsive to the motor current for controlling the opening of said switches.

5. In a motor control system, in combination, a direct current motor of the series type for propelling a vehicle, power conductors, switching means for connecting the motor to the power conductors, switching means for establishing dynamic braking connections for the motor, a plurality of switches for shunting the motor field when dynamic braking is established, and relay means responsive to the motor current for causing the opening of said switches successively.

6. In a motor control system, in combination, a direct current motor of the series type for propelling a vehicle, power conductors, switching means for connecting the motor to the power conductors, switching means for establishing dynamic braking connections for the motor, variable resistance means i'or controlling the motor current, means for shunting the motor field during dynamic braking, and relay means responsive to the motor current for controlling the operation of said field shunting means and said variable resistance means.

7. In a motor control system, in combination, a direct current motor of the series type for propelling a, vehicle, power conductors, switching means for connecting the motor to the power conductors, switching means for establishing dynamic braking connections for the motor, variable resistance means for controlling the motor current, means for shunting the motor field when dynamic braking is established, and relay means responsive to the motor current for controlling the disconnecting of said field shunting means and the operation of said variable resistance means.

8. In a motor control system, in combination, a direct current motor of the series type for propelling a vehicle, power conductors, switching means for connecting the motor to the power conductors, switching means for establishing dynamic braking connections for the motor, variable resistance means for controlling the motor current, a plurality of field shunting switches, and relay means responsive to the motor current for controlling the operation of said switches and said variable resistance means during dynamic braking.

'9. In a motor control system, in combination, a direct current motor of the series type for propelling a, vehicle, power conductors, switching means for connecting the motor to the power conductors, switching means 'for establishing dynamic braking connections for the motor, variable resistance means for controlling the motor current, a plurality of switches for shunting the motor field when dynamic braking is established, and relay means responsive to'the motor current for controlling the opening of said switches and pelling a vehicle, power conductors, switching 1 means for connecting "the. motor to the power conductors, switching means for establishing dynamic braking connections for-the motor, variable resistancemeans, for-controlling the motor current, a plurality of switches for shunting the motor field when dynamic braking is established, and relay. means responsive to the motor current for causing theopening of said switches succes- 12 sively during dynamic braking, the operation of said variable resistance means being dependent upon the opening of the last of said switches.

GEORGE R. PURIFOY.

REFERENCES CITED The following references are of record in the file of this patent:

UNITED STATES PATENTS Number Name Date 1,047,151 Baxter Dec. 1'7, 1912 1,738,433 Jewitt Dec. 3, 1929 

